Area Forecast Discussion
Issued by NWS Medford, OR

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FXUS66 KMFR 271531
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
831 AM PDT Mon Mar 27 2017

.DISCUSSION...27/12Z NAM in.

The northern hemispheric projection shows a wave number of four
around the globe and occasionally hints at a five over the next
several days. This argues for a moderately progressive pattern.
That is indeed what we will get over the next several days.
Overall the pattern looks quite spring like...with weaker storms
driven by low amplitude upper level troughs. The primary storm
track will remain to the north of the area...but there will be
some action down here.

A long wave trough is now moving onshore along the west coast and
the last in a series of short waves is rounding the bottom of the
trough as it moves through. This will support continued shower
activity this morning. Showers will diminish this afternoon as
this system moves out to the east and a long wave ridge builds
into the west coast. The current Winter Weather Advisory for the
Cascades is set to expire at 11 AM this morning and that looks
good at this time.

There will be a break in the action as the ridge dominates the
weather picture. This will bring dry and warmer weather to the
area Monday night into Tuesday. The ridge axis will break to the
east of the area Tuesday night and a strong short wave riding up
the back side of the ridge will move onshore to the north of the
area Wednesday. A warm front will move onshore Tuesday
night...followed by a trailing cold front Wednesday afternoon.
With most of the upper level support remaining to the north...both
fronts will be relatively weak this far south. Even so...most if
not all of the Medford CWA will get some light precipitation
Tuesday night into Wednesday night. A stronger short wave with a
more southerly trajectory will move onshore late Wednesday night
with the long wave trough. This along with short waves diving down
the back side of the trough will support post-frontal showers
lasting into Thursday evening...but shower intensity and coverage
will diminish through the day Thursday.

After that...another long wave ridge will build into the west
coast and this will bring another round of dry and warmer weather
beginning Friday.

&&

.AVIATION...27/12Z TAF CYCLE...Unstable conditions will result in
scattered precipitation this morning. VFR CIGS are expected to be
the predominate condition today. Could not rule out temporary MVFR
CIGS with partial mountain obscurations are possible in showers this
morning, but confidence is not high enough to put these conditions
in the TAF`s. Freezing levels are expected to start out around 4000
feet, then rising to around 5000 feet MSL this afternoon. Confidence
is higher for VFR conditions this afternoon through this evening as
the atmosphere becomes more stable. For now kept VFR CIGS in
tonight, but later shifts may need to evaluate the potential for low
clouds and patchy fog for west side valleys if there`s enough
clearing. -Petrucelli

&&

.MARINE...Updated 200 AM PDT Monday 27 March 2017...West winds will
continue today as weak low pressure remains north of the waters, but
they will remain below advisory criteria. However higher west swell
will move into the waters late this morning through this afternoon
bringing higher seas. The higher seas should remain beyond 10 nm
from shore this morning, but as the higher swell comes in, the inner
waters will then get impacted by small craft conditions. Meanwhile
the outer waters could reach hazardous seas warning criteria with
seas expected to be very steep around 15 feet. Steep seas could
linger through at least Thursday morning. -Petrucelli

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory until 11 AM PDT this morning for
        ORZ027-028.

CA...None.

Pacific Coastal Waters...Small Craft Advisory for hazardous seas
        until 11 AM PDT Thursday for PZZ350-356.
     Hazardous Seas Warning until 11 PM PDT this evening for
        PZZ370-376.
     Small Craft Advisory for hazardous seas until 11 AM PDT Thursday
        for PZZ370-376.

$$

15/15/15


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